1. Technical Field of the Invention
The present invention relates generally to image reproduction apparatus and, more specifically, to an improved method and apparatus by which untacked toner particles are removed from an imaging member.
2. Background Art
The cross-referenced application discloses a method and apparatus for producing images on an imaging member. Such apparatus utilizes a moving imaging member onto which a substantially uniform layer of thermoplastic toner particles is deposited. The toner particles are imagewise heated by a scanning, intensity-modulated laser beam which lightly tacks selected toner particles to the imaging member. Those toner particles which are not tacked to the imaging member (nonselected toner particles) are removed from the imaging member by an electrically biased magnetic brush utilizing "hard" magnetic carrier particles. This produces an image on the imaging member.
As the speed of the imaging member is increased, it is necessary to increase the electrical bias on the magnetic brush and the RPM on the magnetic core in order to assure that substantially all the nonselected toner particles will be removed from the imaging member in one pass. As the electrical bias is increased, "carrier pick-up" starts to occur. "Carrier pick-up" refers to the undesired adhesion or entrapment of carrier particles to the imaging member following contact by the magnetic brush. These unwanted carrier particles will cause defects in image quality. As a result, the speed with which images can be produced is limited. Of course carrier pickup can occur anytime the electrical bias on the magnetic brush is too high, irregardless of imaging member speed.